feat: implement TSIGKey API

[bennetgallein]

Description

Add APIs for the /tsigkeys route:
https://doc.powerdns.com/authoritative/http-api/tsigkey.html#tsigkey-endpoints

More information about TSIG:
https://doc.powerdns.com/authoritative/tsig.html

Motivation and context

TSIGKeys were not implemented

How has this been tested?

testing was done using the local docker containers

Screenshots (if appropriate)

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[bennetgallein]

I'm really struggeling to understand how the API handles updates, like the PUT request is currently just creating new keys all the time, even when I only send the algorithms field.. I've pushed this to my branch here: https://github.com/bennetgallein/powerdns-php/tree/feat/tsig-keys-debug in case someone can help me out getting this working the right way..

[bennetgallein]

Hey Tristan! @trizz

I think I've figured it out - there are some quirks with the way the API works that (imo) don't really make sense. I'll list them below to shed some light:

• Whenever you send the name field, powerdns will clone the key with id and create a copy with the new name, but also giving it a new id, since the id seems to be based on the name (just a dot appended(?)).
• when changing the algorithm the key doesn't change, but when creating it get's generated.. It kinda makes sense but why would one want to update the algo without regenerating the key? :D - I did not test changing the algo and sending an empty key to see if that would trigger a regenerate tho..

I think that's it - lmk if you have any feedback or questions :)